The present invention is directed to an inspection system for ultrasonically inspecting a bore in an elongated shaft, such as the shaft of a turbine or generator rotor.
The rotor shafts of large machines, which are commonly provided with an axial bore, must be subjected to careful inspection, both at the time of manufacture and periodically after they have been placed into use in order to detect flaws which may occur during manufacture or may appear after a certain period of use and which could lead to premature, and possibly catastrophic, failure.
A variety of systems have been proposed and developed for performing various tests, each designed to detect a particular type of flaw. Systems of this type include those which effect ultrasonic inspections and eddy current inspections. Inspections of these types require the displacement of a transducer assembly through the bore, along the rotor axis, together with rotation of the assembly about that axis.
Such systems are described, for example, in U.S. Pat. Nos. 3,960,006, 4,699,008 and 4,757,716.
While the systems disclosed in these patents are capable of producing useful results, they have certain shortcomings. Thus, for example, known systems are not capable of rotating a transducer at a sufficiently constant velocity to permit optimum reading accuracy to be achieved. In addition, the known procedures for calibrating such systems, which must be performed before measurements are taken, are time consuming and can easily introduce certain inaccuracies into the measurement results. Further, in the known systems, proper positioning of the inspection system is a difficult and time consuming operation.